Polypodium glycyrrhiza, or licorice fern, is a member of the Polypodiaceae family, which includes about 1200 species of ferns (Alden 1998). This perennial was given its name because of its licorice flavored rhizome. Native Americans used the strongly flavored rhizome for medicinal purposes, as well as for cooking and for sweetening foods (Pojar and MacKinnon 2004). Licorice fern is an evergreen pteridophyte with oblong pinnate fronds 5-12 inches in length that diminish in size further up the stalk, eventually narrowing into a point. Its leaflets are arranged in an opposite pattern and are bright green in color, shiny, fine-toothed, and broad-based (Alden 1998).
Licorice ferns have two rows of sori on the underside of each leaflet. Although the leaflets and stalk are consistently green, the sori are a golden-yellow color, which makes them stand out from the rest of the plant. During cool or humid weather, the fern’s spores are released in hopes of reproducing in more locations. One of Polypodium glycyrrhiza’s distinctive qualities is the fact that each frond grows separately from a reddish-brown rhizome, as opposed to other ferns, which have multiple fronds growing from one site on a rhizome (Brietzke and Starzomski 2013).
Licorice fern is native to western North America and is concentrated in areas such as southern Alaska, southwestern Yukon Territory, western British Columbia, Washington, Oregon, Idaho, and California. Some researchers (e.g., Klinkenberg 2015) mention the existence of a disjunct population in Arizona, however Flora of North America proposes that these reports were based on misidentified specimens (Flora 2016). Throughout its range, licorice fern generally grows at low elevations below 1,800 feet (Kaczynski 2005). Its preferred locations show that it likes temperate regions that tend to have wet winters and cool, moist summers. Polypodium glycyrrhiza typically grows as an epiphyte on broadleaf trees and rocks in lowlands and can also form sheets over rocks and trees. However, it has also been found to grow on the ground, as well as on fallen trees. Licorice fern is particularly fond of growing on Acer macrophyllum, commonly known as bigleaf maple.
